Electronic Potentiometer - Maker Factory ELECTRONICS EXPERIMENTS BOX Manual

2.55 Electronic potentiometer

Circuit 120: Electronic level control
Setup information
Install the two transistors, the three resistors and the two electrolytic capacitors as shown in Fig. 2.120
followed by a jumper wire. Check the placement on the board again before you start with your experiment
and only then connect the battery.
Experiment
An electronic level control is used to determine the weakening of an audio signal by means of the control
voltage value. In our present case, at 0 V control voltage, the audio signal will be damped by the factor 100;
at -5 V control voltage will be muted by Factor 2. The maximum output voltage is about 1 V. As sources for
the (negative) control voltage you could use batteries such as 1.5V, 3V, 4.5V batteries or a suitable variable
power supply.
The circuit diagram for this experiment is shown in Chap. 3, Fig. 3.120.
Components required:
1 x J111 FET transistor,
1 x 220 kΩ resistor,
1 x 100 Ω resistor,
1 x 10 kΩ resistor,
1 x 10 μF electro-
lytic capacitor,
1 x breadboard, 1 x 9V
battery with clip con-
nector
Fig. 2.120: Electronic level
control
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